Geared drives incorporating fluid couplings

ABSTRACT

A double-circuit fluid coupling has a rotating outer casing formed in two similar halves between which is clamped an internal flange of a gear rim formed with wide external gear teeth. Only the middle portions of the gear ring and casing are in contact while the axially outer portions are spaced by air gaps from the casing to form a much longer heat path from the coupling circuits to the gear rim and thereby prevent distortion of the gear rim as the result of uneven expansion due to sudden heat generation in the working circuits during maneuvring.

United States Patent Bilton 1 Sept. 12, 1972 54] GEAREDDRIVESINCORPORATING FLUID COUPLINGS [72] Inventor: John Bilton, Hampton,England [73] Assignee: Fluidrive Engineering Company Limited, Middlesex,England [22] Filed: May 12, 1971 [21] Appl. No.: 142,682

[30] Foreign Application Priority Data May 13, 1970 Great Britain..23,240/70 [52] US. Cl. ..74/730, 60/54, 74/431, 74/665 B [51] Int. Cl..F16h 47/06, F16d 33/00, F16h 57/04 [58] Field of Search .....74/730,431, 432, 433; 60/54 [56] References Cited UNITED STATES PATENTS2,298,310 10/1942 Ray ..60/54 2,465,919 3/1949 Novak ..60/54 2,549,5574/ 1951 Yancho et a1. ..60/54 2,585,968 2/1952 Schneider ..60/54 x2,588,668 3/1952 Syrovy ..60/54 FOREIGN PATENTS OR APPLICATIONS1,157,849 7/1969 Great Britain ..60/54 Primary Examiner-Carlton R;Croyle Assistant Examiner-Thomas C. Perry AttorneyWoodhams, Blanchard &Flynn [57] ABSTRACT A double-circuit fluid coupling has a rotating outercasing formed in two similar halves between which is clamped an internalflange of a gear rim formed with wide external gear teeth, Only themiddle portions of the gear ring and casing are in contact while theaxially outer portions are spaced by air gaps from the casing to form amuch longer heat path from the coupling circuits to the gear rim andthereby prevent distortion of the gear rim as the result of unevenexpansion dueto sudden heat generation in the working circuits duringmaneuvring.

6 Claims, 6 Drawing Figures PATENTED EP 2 2 3.690.196

sum 2 [IF 5 MLZQM W nrfam PATENTEDSEP 12 I972 3.690.196

saw u I]? 5 GEARED DRIVES INCORPORATE G FLUID COUPLDIGS This inventionrelates to high-powered geared drives incorporating fluid couplings, forexample marine propulsion drives transmitting say 25,000 h.p.

The pinions and gear wheels of such drives are necessarily wide(measured in the direction of the axis of rotation) in order to transmitthe high power without excessive tooth loading. Moreover, the gear teethmust be very accurately formed in order to ensure substantially uniformload distribution over the gear teeth as they mesh in order to avoidlocalized overloading. It is found in practice that variations in thegear tooth profiles over quite small lengths of the teeth by fractionsof a thousandth of an inch can cause large alterations in the localloading of the tooth and can therefore completely upset the uniformtooth loading which is desired along the full width of the gear wheel.

In addition to the width of the gear wheel itself, measured in the axialdirection, further length is required to accommodate the supportingbearings for the gear wheel. The incorporation of fluid couplings intothe drive in the conventional manner as shown for example in BritishPat. specification No. 1,076,273 would obviously further increase thelength of the fluid coupling and gear wheel assembly. In many cases,particularly in the case of warships, theoverall length of such a driveis undesirable or even unacceptable. In order-to provide a more compactdrive, it has already been suggested that in the case of relativelysmall drives, at most of the order of a few hundred horsepower, a gearwheel rim should be secured to the rotating casing of a fluid coupling.An example of such an arrangement is shown in US. Pat. specification No.1,979,930.

Problems arise however in applying this arrangement to high powerdrives.

In order to reduce the overall radial demensions of high power fluidcouplings, it is known to use a double circuit coupling in which twointerconnected. inner vaned elements, one foreach working circuit, faceoutwards away from each other and each form one element of therespective working circuit and the other two vaned elements face inwardsand are interconnected by a casing enclosing the inner elements.

With this arrangement, it would appear that the casing could form thegear ring itself or that a separate toothed gear rim could beshrink-fitted onto it.

However, in accordance with the present invention, the gear wheel rimand easing are secured together only in the middle regions of the gearwheel rim and the casing in such a manner that the axial end portions ofthe gear wheel rim are spaced from the casing by an air This arrangementavoids the risk of heat generated in the coupling working circuits beingdirectly conducted to one portion of the gear wheel very rapidly beforeother portions have the chance to reach equivalent temperatures.

Where the fluid couplings are selectively filled or emptied to selectforward or reverse drive, abnormally high temperatures may be reachedwithin the coupling over a short period during a crash change fromforward astern drive or vice versa in a ship. Even though largequantities of liquid are circulated through the coupling for coolingpurposes, for example 1,000 gallons per minute, the reversal of a 25,000h.p. drive can generate so much heat that the temperature within thecoupling may rise by about 230 F. to a final temperature of over 300 F.

With the arrangement of the invention, the air gaps between the two endsof the gear wheel rim and the outer casing of the coupling act as heatbarriers so that the conduction path for heat from the outer portions ofthe coupling working circuits to the gear wheel rim is a relatively longpath extending from an end of the casing to the middle and then upwardsagain through the gear wheel rim. By this means the rapid high rise intemperature is reduced and heat is transferred from the casing to themiddle of the gear wheel rim at a lower rate such that it can be spreadthrough virtually the whole of the gear wheel rim much more uniformlythan if the whole of the gear wheel rim where in thermal contact withthe casing.

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 shows an axial sectional view of a combined double circuit fluidcoupling and gear wheel rim incorporated in reduction gearing,

FIG. 2 shows a detail of 1 on an enlarged scale,

FIG. 3 is a diagrammatic end view of a. marine propulsion systemincorporating such a combined fluid coupling and gear wheel assembly, 7

FIG. 4 is an elevational view seen in the direction of the arrows IV-IVof FIG. 3, and

FIGS. 5 and 6 are views similar to FIGS. 3 and 4 respectively of anothermarine propulsion system, in-

corporating the assembly shown in FIGS. 1 and 2.

The double circuit coupling and gear wheel assembly shown in FIGS. 1 and2 comprises two vaned impeller elements 1 and 2 and two vaned runnerelements 3 and 4 which are secured back-to-back. The elements 1 and 3together define a first toroidal working circuit W while the elements 2and 4 define a second toroidal working circuit W Suitable means 8,, Sare provided for supplying working liquid to the working circuits W andW so as to maintain them filled when drive is to be transmitted from theimpellers l and.2 to the runners 3 and 4. Provision is also made foremptying the working circuits when the drive is to be discontinued andfor maintaining a flow of the working liquid for cooling purposes whilethe drive is being transmitted. These results may be achieved byconventional methods.

The runners l and 2 form the ends of a casing 6 for the coupling whichincludes two identical generally cylindrical portions 7 and 8 bolted toflanges 9 and 10 on the impellers l and 2 at 11 and 12 respectively. Theaxially inner ends of the casing portions 7 and 8 have inwardly directedflanges 13 and 114 between which is clamped an inwardly-directed centralflange 15 of a symmetrical gear wheel rim 16 formed with long helicalgear teeth 17. The flanges 13, 14 and 15 are clamped tightly together bya ring of bolts 18.

Adjacent the root of the flange 15, the gear wheel rim 16 has twocylindrical seating surfaces 19 and 20 which engage correspondingclearance spigot surfaces on the casing portions 7 and 8 to provideinitial support for the gear wheel rim 16 during assembly. After thegear wheel rim 16 has been accurately positioned, holes are reamedthrough the flanges I3, 14 and 15 to accommodate dowel pins (not shown).As is clearly shown in FIG. 1, the remainder of the length of the gearwheel rim 16 is spaced from the adjacent casing portions 7 and 8 by airgaps 21 and 22. As a result, the heat conduction path from the workingcircuits W and W to the gear wheel rim 16 is long. Supposing for examplethat the working circuit W and W, are empty and that the impellers 1 and2 are rotating in the opposite direction to that of the runners 3 and 4.If the working circuit W and W are suddenly filled, a large amount ofheat will be rapidly generated in the working circuits and as a resultarresting the machinery components attached to the runners 3 and 4,including the propeller shaft and propeller, and in accelerating them inthe direction of rotation of the impellers 1 and 2.

As mentioned above, the temperature rise may be as high as 230 F. If thegear wheel rim 16 were indirect thermal contact with the casing portions7 and 8 along the whole length of the gear wheel rim, the rapidtemperature rise would be conducted first of all to the two ends of thegear wheel rim, at which stage the two end portions would begin toexpand while the relatively cool center portions of the gear wheel rimretain their normal dimensions. In this way, the very accurately formedhelical tooth profile would be distorted and the entire tooth loadingwould be concentrated over the high spots and thus over a relativelysmall proportion of the total tooth length. Serious damage would beinevitable.

fith the arrangement shown in FIGS. 1 and 2, the rapid temperature risefrom the working circuits cannot reach any of the gear wheel rim 16until it has been conducted through the casing portions 7 and 8 to theflange 15. Accordingly, the rate of rise of temperature at the flangewill be less than at the outer ends of the casing portion 7 and 8.Moreover, the temperature rise is applied to the gear wheel rim over arelatively large area and at a relatively thick portion of the gearwheel rim so that the heat conduction path to all parts of the gearwheel rim is comparatively short. Thus the rate of increase intemperature is reduced by the casing portion 7 and 8 and is well spreadover the whole length of the gear wheel rim.

. The underside of the gear wheel rim 16 where it forms one surface ofthe air gap 31 and 32 may be profiled to control the rigidity of thegear wheel rim in such a manner that satisfactory tooth contact isachieved over the full length of the gear wheel rim in service. Thisprofile may be initially calculated and checked by initial trials whenthe actual degree of tooth bedding can be visually checked. Thereafterany slight modifications to the profile can be made.

The marine power transmission shown in FIGS. 3 and 4 comprises an outputbull wheel 31 secured to the propeller shaft 32. The hull wheel 31 is tobe driven selectively in forward or reverse direction from twounidirectional turbine shafts 33A and 33B. The shaft 33A carries apinion 34A which meshes with an ahead wheel 35A and with the gear wheelrim of a fluid coupling and gear wheel assembly 36A of the kind shown inFIGS. 1 and 2. The coupling and gear wheel assembly 36A also meshes withan astem coupling and gear wheel assembly 37A of similar construction.

The ahead wheel 35A is connectable with a shaft 38A by means of a dogclutch 39A. The shaft 38A carries a pinion 40A which meshes with thebull wheel 31. A shaft 41A carries a pinion 42A which also meshes withthe bull wheel 31. The shaft 41A extends through the ahead coupling andgear wheel assembly to carry a synchronous self-shifting clutch 43Ahaving a control member 44A. The other part of the S.S.S. clutch 43A issecured to a hollow shaft 45A which in turn is secured to the two runnerelements of the ahead assembly 36A. The moving elements of the dogclutch 39A and the control sleeve 44A of the SSS. clutch 43A are linkedby a lever 46A pivoted at 47A. With this arrangement, the dog clutch 39Acannot attempt to engage until the SSS. clutch detects synchronismbetween the shafts 45A and 41A during filling of the working circuit ofthe ahead assembly 36A.

In operation, ahead drive is engaged by emptying the working circuit ofthe astem coupling and gear wheel assembly 37A and thereafter fillingthe working circuits of the ahead assembly 36A until the clutches 43Aand 39A can be engaged. The power flow from the turbine shaft 33A to thebull wheel 31 is then shared by the two shafts 41A and 38A.

To engage astem drive, the speed of the turbine shaft 33A is temporarilyreduced to unload the clutches 39A and 43A. At the same time the workingcircuits of the ahead assembly 36A are emptied and the working circuitsof the astem assembly 37A are filled. The gear wheel rim of the aheadassembly 36A then acts as an idler wheel to transmit power from theworking shaft 33A to the astem assembly 37A, the output shaft 48A ofwhich carries a pinion 49A meshing with the bull wheel 31.

In the marine propulsion system shown in FIGS. 5 and 6, each turbineshaft is coupled to an input shaft 51, 52 carrying a pinion 53, 54respectively. The pinion 53-meshes with'the gear wheel rims of two aheadgear wheel and coupling assemblies 55 and 56 of the kind shown in FIGS.1 and 2, the assembly 55 being that shown in FIGS. 1 and 2. The pinion54 meshes with two further coupling and gear wheel assemblies 57 and 58.The output of each of the four coupling and gear wheel assemblies 55,56, 57 and 58 is connected to a respective pinion 60, 61, 62, 63 all ofwhich mesh with a common bull wheel 64.

A fifth coupling and gear wheel assembly 65 meshes with the twoassemblies 56 and 57 to provide an astem drive through a pinion 66 whenits working circuits are filled and thus all the four ahead couplings55, 56, 57 and 58 are emptied. The astem pinion 66 also meshes with thebull wheel 64.

Where the turbines are gas turbines, the input shafts 51 and 52 mayrotate at 5,660 rpm and the gear wheel rims of each of the fourassemblies 55 to 58 may then be arranged to rotate at 1,560 rpm whilethe astem gear wheel rim may rotate at 1,600 rpm. If each gas turbineproduces 25,000 h.p. each ahead coupling and gear wheel assembly willtransmit 12,500 h.p. and may be designed to be of a size such that theminimum slip under normal conditions is no more than 1% percent.Preferably, an over-running or disconnectible clutch is provided betweeneach turbine and the respective pinion 53 and 54 to enable one turbineto run while the other is stationary, for example for repairs ormaintenance.

It will be appreciated that the gear wheel rim of the astern assembly 65interconnects the two input pinions 53 and 54 through the gear wheelrims of the assemblies 56 and 57. Thus, when one turbine is out ofservice the drive from the other turbine is distributed over all fourahead coupling assemblies. Even if the two fluid coupling assembliesassociated with the idle turbine are emptied the slip in the tworemaining coupling assemblies would still be only about 2% percent.

While the temperature rise in the ahead couplings during maneouvring isreduced by the using of four ahead couplings, the temperature rise inthe single astern coupling could still be serious if the astern assemblydid not incorporate the features of the invention. Moreover, in order toreduce the total oil flow demanded from the filling pump system durintfilling of the ahead couplings in a change to forward drive, the fillingsystem may be arranged so that one fluid coupling assembly (e.g., 55)fills substantially before the other fluid coupling assembly (e.g., 56)associated with the same turbine. The application of the features of theinvention to the ahead coupling assembles avoids the overheating problemduring such a change to ahead drive. At the same time, by more quicklyfilling one coupling, the overall time required to effect a change inthe direction of drive is reduced.

As can be seen from FIGS. 2 and 3 and from FIGS. 4 and 5, the use of thecombined fluid coupling and gear wheel assemblies enables the overalllength of the transmission and hence the size of its casing to bematerially reduced.

I claim:

ii. In combination, a double-circuit fluid coupling and a gear ring,each circuit of said fluid coupling being defined by a first vanedmember and a second vaned member, the two first vaned members beingsecured in back-to-back relationship, with casing means interconnectingthe two second vaned members and enclosing the two first vaned members,wherein the gear ring is secured to said casing means only in the middleregions respectively of said gear ring and said casing so as to defineair spaces between said casing means and the axially outer portions ofsaid gear ring.

2. The combination set forth in claim 1, in which the axially outerportions of said gear ring are of progressively reduced radial thicknesswith decreasing distance from the ends of said gear ring.

3. The combination set forth in claim 2, in which the external surfaceportions of said casing means underlying the axially outer portions ofsaid gear ring are correspondingly shaped so that said air spaces areannular and substantially parallel-sided.

4. The combination set forth in claim 1 in which said gear ring, saidcasing means and the two working circuits of said coupling aresymmetrically disposed about a common median plane of the coupling andgear ring.

5. The combination set forth in claim 4, in which said I gear ring has acentral internal flange and said flange is clamped between substantiallyidentical casing portions of said casing means.

6. The combination set forth in claim 2, in which said gear ring, saidcasing means and .the two workingcircuits of said coupling aresymmetrically disposed about a common median plane of the coupling andgear ring.

1. In combination, a double-circuit fluid coupling and a gear ring, eachcircuit of said fluid coupling being defined by a first vaned member anda second vaned member, the two first vaned members being secured inback-to-back relationship, with casing means interconnecting the twosecond vaned members and enclosing the two first vaned members, whereinthe gear ring is secured to said casing means only in the middle regionsrespectively of said gear ring and said casing so as to define airspaces between said casing means and the axially outer portions of saidgear ring.
 2. The combination set forth in claim 1, in which the axiallyouter portions of said gear ring are of progressively reduced radialthickness with decreasing distance from the ends of said gear ring. 3.The combination set forth in claim 2, in which the external surfaceportions of said casing means underlying the axially outer portions ofsaid gear ring are correspondingly shaped so that said air spaces areannular and substantially parallel-sided.
 4. The combination set forthin claim 1 in which said gear ring, said casing means and the twoworking circuits of said coupling are symmetrically disposed about acommon median plane of the coupling and gear ring.
 5. The combinationset forth in claim 4, in which said gear ring has a central internalflange and said flange is clamped between substantially identical casingportions of said casing means.
 6. The combination set forth in claim 2,in which said gear ring, said casing means and the two workingcircuitsof said coupling are symmetrically disposed about a common median planeof the coupling and gear ring.